Modern Melanesians have retained Denisovan DNA

Modern Melanesians harbor genetic components passed on from Denisovans, a new study suggests. In the past, ancestors of many modern human populations interbred with other hominin species that have since become extinct, such as the Neandertals and Denisovans. Mapping the gene flow of surviving genetic sequences from these species, as well as other species of hominin, helps shed light on how past interbreeding has affected human evolution. While previous studies have documented Neandertal gene flow in modern humans, much less is known about the characteristics of Denisovan DNA that persist in humans today. To gain more insights, Benjamin Vernot et al. analyzed the genomes of 1,523 individuals from around the world, including 35 individuals from Northern Island Melanesia, in Papua New Guinea. Their results showed that while all non-African populations surveyed inherited roughly 1.5-4% of their genomes from Neandertals, Melanesians were the only population that also had significant Denisovan genetic ancestry, representing between 1.9% and 3.4% of their genome. The researchers then mapped out the genetic flow of Neandertal and Denisovan sequences, finding that Neandertal admixture, or gene flow, occurred at least three distinct times in modern human history. In contrast, Denisovan admixture likely only occurred once. Further analysis revealed that certain regions of the modern human genome are particularly depleted of these archaic lineages, including those that play a role in the developing cortex and adult striatum. These findings provide new insights into human evolution and gene flow.